Some conventionally known pressure regulators operate in a mode of operation known as “fail open”. Such “fail open” regulators include a spring biased against a diaphragm in such a way that failure of the diaphragm (such as through rupture) causes the regulator to remain open allowing an unregulated flow of fluid. Other conventionally known pressure regulators operate in a mode known as “fail closed”, wherein the spring is biased against the diaphragm in such a way that failure of the diaphragm causes the regulator to close, preventing any flow of fluid. Yet other conventionally known pressure regulators are merely operating control valves in a fixed position, such that failure of the regulator does not open or close the regulator. Essentially, all conventional pressure regulators operate by sensing the downstream pressure and controlling the flow of fluid based upon the downstream pressure. Thus, all conventional pressure regulators also utilize a sensor positioned at a downstream location and in communication with the regulator through a sensor transmission line.
With reference to FIG. 1, a conventional dual port “fail open” type of pressure regulator system 10 is shown having a diaphragm 12, a spring 14, a rod 16, an annular pipe 22, and first and second seats 38 and 42. The spring 14 is loaded to exert a force on the diaphragm 12 corresponding to a desired outlet pressure P2 within an outlet conduit 36. The rod 16 includes a collar 18 connected to the pipe 22. While an annular pipe 22 is shown, it should be appreciated that any form of pipe with or without an annulus, including for example, a rod or a piston, may be used. Further, although a dual port regulator system is shown, it should be appreciated that a single port regulator system may be used.
The pressure regulator 10 is illustrated in the open position. In operation, the pressure regulator 10 reduces an inlet gas pressure P1 within an inlet conduit 32 to the outlet gas pressure P2 by bleeding gas past apertures 40 and 44. In normal operation, while the outlet gas pressure P2 is below a certain threshold amount, the diaphragm 12 and the spring 14 exert a biasing force through the rod 16 and the collar 18 onto the annular pipe 22 and the seats 38 and 42, pushing and maintaining the seats 38 and 42 out of sealing arrangement with the apertures 40 and 44.
Upon the downstream or outlet gas pressure P2 exceeding a desired level, the pressure regulator 10 closes or restricts the apertures 40 and 44 by moving sealing surfaces 46a and 46b of, respectively, seats 38 and 42, into sealing contact with the apertures 40 and 44 of the conduit 32, thereby closing off the source of P1.
A disadvantage to the conventional pressure regulator systems, such as the system illustrated in FIG. 1, is that such systems could be intentionally tampered with or unintentionally adjusted improperly. For example, if the sensor transmission line were sabotaged, i.e. cut, the pressure regulator system would not be able to determine an increase in the downstream P2. Instead, the pressure regulator would read a zero value for the downstream P2. In addition, the maximum pressure set point of such systems can be affected by pressure from the environment. Further, pressure regulators are often positioned in underground vaults nearby piping, and in circumstances where flooding of the underground vaults has occurred, increased pressure on the exterior of the chamber holding the diaphragm 12 (from the hydrostatic head of the flooding) counteracts the pressure from the spring 14, resulting in an improperly functioning diaphragm 12. In these undesired states, outlet pressures higher than those desired for normal operation are delivered, which has the potential for adverse results.